18 out of 40 healthy Danish type A haemophiliacs had antibodies against HTLV‐III as measured by an enzyme linked immunosorbent assay (ELISA). The overall seropositivity was 45%. A significant positive correlation was found between seropositivity and total lifetime dose of factor VIII and the age of the patients. 63% and 79% of the patients predominantly treated with commercial American and European preparations, respectively, had antibodies, compared with 11% among patients predominantly treated with Danish cryoprecipitate. Patients exclusively treated with preparations from a single source in the year prior to investigation showed 69% seropositivity when treated with American and European preparations. None of the patients treated with Danish cryoprecipitates prepared from voluntary Danish donors had antibodies. No difference between seropositive and seronegative groups was found in total lymphocyte count, leu 2+ cells, leu 3 + cells and leu 2 +/leu 3 + ratio, but the seropositive group had significantly higher total IgG and lower skin test score. It is concluded that treatment with local European preparation carries less risk of HTLV‐III infection compared with commercial preparations from either the USA or Europe. The results also suggested that T‐cell subset alterations among haemophiliacs are not primarily due to HTLV‐III infection.